The field of the present invention is the processes and apparatus for splitting pistachios which have not opened naturally.
Pistachios are the seed of a small tree of the cashew family. They are referred to as nuts and they come in a hard smooth shell. This shell tends to split along one side when the nut matures. A, a significant portion of the harvested nuts are not naturally split. However, the consumer market demands nuts with the shells split.
Mechanisms have been devised for separating the split nuts from those where the shell has not split. One such mechanism includes a large slowly rotating drum with short fine rigid wires extending into the drum. The split shells become hooked on the wires and ride up on the rotating drum to a higher level than the nuts which have not become hooked. A collector placed upwardly in the drum is positioned to collect the hooked nuts which ultimately fall from the surface of the drum as the drum arches over toward the uppermost position thereof. The unsplit nuts remain in the bottom of the drum and ultimately work their way to the other end. These unsplit nuts are separately collected.
The value of the unsplit pistachios is significantly less than that of the naturally split nuts. To enhance the value of the unsplit nuts, they may be artificially split. A number of ways have been devised for artificially splitting pistachios.
From early times through the present, pistachios have been hand split. Currently it has been found economical to ship the nuts from the United States to China for hand splitting and then return them for sale at a higher price. Many hand devices are understood to be used such as pliers and the like to squeeze the nut until it splits.
Another mechanism which has been devised is to pass the nuts through a tapered area between a rotating conical mandrel and a concentrically arranged cylinder. The nuts must be distorted in compression to pass beyond the mandrel. This distortion is intended to split the nut artificially.
A more promising method has been devised which includes moisturizing the unsplit nuts to soften the shells, making them more resilient. The pistachios with softened shells are then released from the moisturizer and fed to a splitter. Such splitters employ bins for receiving the nuts. The nuts are fed to singulators which include horizontal troughs. A slide plate is positioned in the bottom of the trough and has holes of a size able to receive an individual pistachio. The slide plate has two positions. The first position is with the holes underneath the trough so as to receive nuts retained within the trough. The second position is with the holes outwardly of the trough and above an inclined plate such that the nuts may drop through the holes in the slide plate to the splitter mechanism. The slide plate then returns to the first position to pick up more nuts such that the process may be repeated.
The singulated nuns drop into individual cradles which are U-shaped in cross section and have an elongate axis extending between a movable splitting head and a stationary splitting jaw. Once the singulator has cycled so as to release individual nuts into the cradles, the movable splitting head is moved toward the splitting jaw. The softened shells of the pistachio nuts are split by the pressure placed on the ends. Once split, the cradles are pulled from beneath the nuts to fall on conveying mechanisms. The nuts are then dried and otherwise processed for sale.
Some difficulties have arisen with the last-mentioned mechanism. The moisturizing is most conveniently done in batches. Consequently, the softened nuts are presented to the splitting mechanism in surges. The surges have been found to alternately overpack or starve the singulator such that the mechanism does not operate efficiently. Further, the nuts presented to the cradles can land haphazardly and also can slide from position during the splitting process. The moisturizing process can also result in the colored membrane of the nut breaking up and sticking to the outside shell. The moisture involved causes the membrane to bleed onto the shell which is of sufficient porosity to receive the color. Consequently, the nuts can take on an unsightly appearance.